Field of the Invention
The present invention relates to an automatic transmission for vehicles, and more particularly, to a planetary gear train of an automatic transmission for vehicles, which can improve a power transmission capability and enhance fuel efficiency by implementing at least ten forward speeds by a minimum number of components and improve driving silence of a vehicle by using an operating point at a low rpm region of an engine.
Description of Related Art
In general, in the automatic transmission field, more shift-stages as a technology for improving fuel efficiency of a vehicle and maximizing drivability has been researched. Recent increases in oil prices are triggering stiff competition in enhancing fuel consumption of a vehicle. As a result, in the case of an engine, research for reducing a weight and enhancing the fuel efficiency through downsizing has been conducted and in the case of an automatic transmission, research which can secure both drivability and fuel efficiency competitiveness through more shift-stages has been conducted.
However, in the case of the automatic transmission, as the number of shift-stages increases, the number of internal components (particularly, planetary gear sets) increase, and as a result, a length of the transmission increases. This may deteriorate installability and/or power flow efficiency and may increase production cost, and weight. Accordingly, in the case of the automatic transmission, development of a planetary gear train which may bring about maximum efficiency with a small number of components is important in order to increase a fuel efficiency enhancement effect through the more shift-stages.
In this aspect, in recent years, the automatic transmission has been configured to implement a transmission of eight-speeds or more to be mounted on the vehicle and research and development of a planetary gear train capable of implementing a shift-stage of eight speeds or more have also been continuously required.
However, most general automatic transmissions of eight speeds or more generally include 3 to 4 planetary gear sets and 5 to 6 control elements (friction elements) and in this case, the whole length increases, and as a result, the mountability is likely to deteriorate.
As a result, in order to make the shift-stages (speed stages) of the automatic transmission into the multiple speed-stages, in recent years, a double row structure that arranges one planetary gear set on another planetary gear set has been adopted, or a dog clutch has been applied instead of a wetting control element, but in this case, an applicable structure is limited and deterioration of shift quality due to the application of the dog clutch is accompanied.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.